Windows DHCP Client: Denial of service through memory leak
Summary
A missing memory release in the Windows DHCP Client allows an unauthorized attacker to cause a denial of service over the network. Affected are Windows 11 (24H2, 25H2, 26H1, 26H2) and Windows Server 2025, including Server Core. The impact is availability only; confidentiality and integrity are not affected. Because DHCP traffic normally stays on the local network segment, the realistic attacker is someone on the LAN or Wi-Fi.
Affected
- Windows 11 Version 24H2 (10.0.26100.0 to below 10.0.26100.9711)
- Windows 11 Version 25H2 (10.0.26200.0 to below 10.0.26200.9711)
- Windows 11 Version 26H1 (10.0.28000.0 to below 10.0.28000.3231)
- Windows 11 Version 26H2 (10.0.26300.0 to below 10.0.26300.9711)
- Windows Server 2025 and Server Core installation (10.0.26100.0 to below 10.0.26100.33650)
Fixed in
- Windows 11 24H2: 10.0.26100.9711 (Microsoft's October 2026 security update)
- Windows 11 25H2: 10.0.26200.9711
- Windows 11 26H1: 10.0.28000.3231 (KB5127646 according to Tenable listings, not verified on MSRC)
- Windows 11 26H2: 10.0.26300.9711
- Windows Server 2025: 10.0.26100.33650 (KB5126646 according to Tenable listings, not verified on MSRC; the build number comes only from a third-party mirror)
- KB numbers for 24H2 and 25H2: Unknown.
Workaround
Unknown. No workaround or mitigation is documented in the CVE record or in the sources reviewed.
Exploitation
- Microsoft rates exploit code maturity as Unproven (E:U).
- No exploitation in the wild found; CISA SSVC lists exploitation as none and the issue as automatable.
- EPSS score is low (0.01125).
- No public proof of concept found; this is absence of evidence, not proof that none exists.
Our recommendation
- Check the affected Windows 11 and Server 2025 versions in your fleet, including versions not listed in the CPE entry (25H2, 26H1, 26H2, Server 2025).
- Install Microsoft's October 2026 security update, prioritizing servers and critical clients; check the KB numbers on the MSRC page first.
- Monitor endpoints for DHCP client outages or unusual memory growth.
- Limit untrusted devices on the LAN and Wi-Fi segments.
- Confirm that this entry (CVE-2026-83677) is the one that applies; do not confuse it with CVE-2026-69781.
Information from Microsoft (Patch Tuesday October 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Microsoft Security Update Guide: CVE-2026-83677 msrc.microsoft.com
- Vulners CVE record (CVELIST mirror of CVE.org) vulners.com
- Vulners NVD record (including EPSS and Tenable KB listings) vulners.com
- OpenCVE record app.opencve.io
- Strix.ai mirror (third-party, build number to verify) www.strix.ai
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 2 Nov 2026, 18:47.
Original description (NVD)
Missing release of memory after effective lifetime in Windows DHCP Client allows an unauthorized attacker to deny service over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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